Effects Of Drought To Absorptive Root Traits And Growth Of 4 Tree Species In Subtropical China

The research is about the responses of different-diameter absorptive root traits of 4subtropical broad-leaved tree species seedlings,including two fine-root tree species?Schima superba,Elaeocarpus sylvestris?and two coarse-root tree species?Cinnamomum camphora,Michelia chapensis?to drought through greenhouse cultivation.The research was divided into control?CK,with soil volumetric water content as 20.3+2.6%?,moderate drought stress treatment?D1,85%irrigation water as CK?and severe drought stress treatment?D2,70%irrigation water as CK?with 4replicas of each treatment.The research contents are as follows:Morphology,anatomy,chemistry and physiology of absorptive roots under water stress;the soil nutrients,soil microorganism activity of rhizosphere soil,mycorrhizal infection rate,external root hyphal length and seedling growth.The results and conclusions of this study will contribute to our understanding of patterns and mechanisms of plant physiology and the adaptation capacity of woody plants to water stress.This also represents an important step further in studying the relation between root traits and ecosystem functions and will contribute to the afforestation and forests transforming in Subtropical China.The results showed that:?1?The functional traits of fine roots in different tree species were significantly different under different environmental conditions.Drought stress on absorptive roots of S.superba branch ratio and specific surface area had a significant effect?P<0.05?.Compared with CK,D1 and D2 of branch ratio were reduced by 17.1%and 25.0%respectively,and the specific surface area increased by 25.9%and 15.0%respectively.?2?Plants absorb nutrients and moisture primarily through their roots.There are different strategies for nutrient uptake between the coarse-root and fine-root plants.Drought reduced the mycorrhiza infection rate of 1^st order roots of coarse-root plants,in this study,C.camphora CK and D1 root infection rate were 0.5%and 0.3%,M.chapensis CK,D1 and D2 root infection rate were 1.7%,1.2%and 0.4%respectively.In this study,two kinds of fine-root plants?S.superba and E.sylvestris?were affected to the low levels by fungal infection,which also had not found root infection in 1^st order roots.?3?The drought stress on soil microbial activity had a significant inhibitory effect.After one year of drought treatment,the amount of microbial carbon in the root soil of 4 tree species decreased.M.chapensis D1 and D2 were significantly reduced by 12.2%and 17.7%comepare with CK,but the influence of S.superba,E.sylvestris and C.camphora were not significant?P<0.05?.The effects of drought to soil enzymatic activity of fine-root plants are stronger than those of coarse-root plants.In different seasons,drought stress can cause the inhibition significantly of the soil enzymatic activity of S.superba and E.sylvestris?P<0.05?,while the influence of C.camphora and M.chapensis were not significant.According to drought treatment in March 2017,comepare with CK,the soil urease and invertase activity of E.sylvestris D1 reduced by 27.5%and 26.9%respectively,S.superba D1?D2 increased by 1.2%?reduced by 27.4%and 6.3%?49.0%respectively.According to drought treatment in June 2017,comepare with CK,the soil urease and invertase activity of S.superba reduced by 12.4%?11.8%and 18.1%?25.5%respectively.According to drought treatment in September 2017,comepare with CK,the soil urease and invertase activity of S.superba fell by 12.4%?11.8%and 18.1%?25.5%respectively.?4?The effects of drought on plant height and basal diameter of fine-root plants are higher than those of coarse-root plants.The growth rate of basal diameter of E.sylvestris decreased significantly?P<0.05?,the basal diameter of CK and D1 was risen by 26.2%and 17.1%respectively,S.superba CK,D1 and D2 increased 2.6%,9.8%and 4.0%respectively,C.camphora CK and D1 increased by 8.8%and 9.4%respectively,M.chapensis CK,D1 and D2 increased 15.7%,5.3%and 8.2%respectively.Drought stress has significantly reduced the growth rate of S.superba height?P<0.05?.After one year of drought treatment,S.superba CK,D1 was risen by34.3%,29.0%and 4.3%.In the meantime,E.sylvestris CK and D1 increased by 7.0%and 3.4%respectively,C.camphora CK and D1 increased by 20.2%and 10.7%respectively,M.chapensis CK,D1 and D2 g increased by 14.5%,15.8%and 11.7%respectively.